From what you had mentioned..if it is exactly the way it is..she is clearly taking advantage and shuns her responsibilities. She is the mother and she had to take care.getting Help is one thing but she is overdoing. Try toTell her next time,that your legs are aching,body aching and you would love to have nephew with you but since you want to sleep and take rest,you are unable to care..keep giving reasons. Try to get some hobby classes in the afternoon and leave home for an hour or so. How is her hubby okay with that?Does he know what his wife is doing? Again..as Rihana said,she might be tackling challenges as such health or other issues and so terming her irresponsible might not be right. However..she should find other help by paying money and not you all the time.That is the problem. Sometimes,people unintentionally also make mistakes.She might have thought “family” so it is ok.Hence,figure out before taking action.